This invention pertains to the display of a multiplicity of moving objects on a raster scan display during the play of an electronic video game. More particularly, this invention relates to a method and inexpensive implementing display circuitry for producing signals for controlling the display of a large number of objects on a color TV monitor in a game controlled, for example, by a microprocessor.
The approach taken earlier in microprocessor-based video game displays has been to create a memory "map" by writing into a memory information defining an entire frame to be displayed, as discussed in U.S. Pat. No. 4,177,462 issued to Chung. Chung attempts to liberate the game microprocessor from the arduous and very time-consuming task of preparing a memory map. He is thereby able to achieve a substantially improved capability for displaying and moving substantial numbers of objects on a screen. Chung's invention does, however, continue to impose severe constraints upon the game microprocessor. Chung permits game control information to be placed in the permanent memory of the game display, thereby requiring extensive communication between the game microprocessor and the display circuitry. Furthermore, he requires that both the game microprocessor and the display circuitry operate synchronously off a single clock. The game microprocessor must become inactive during all communication periods and therefore time is taken or "stolen" from the game microprocessor's available time for performing game-associated computations. Finally, Chung discloses a construction using content addressable memories which are highly specialized, and therefore expensive, devices.
The objects of the present invention may be accomplished by using high speed processor means for keeping track of video screen locations where objects are to be displayed. Signals that cause the display of the particular object are then read out of a permanent memory at the time the signals are needed to control the color gun and intensity amplifiers which, in turn, control the monitor. A specific construction of an embodiment of the high speed processor means is disclosed in the present applicant's concurrently filed application entitled "High Speed CPU/sequencer for Video Games."
The method and circuitry are of very general application. The generality results in part from the need for limiting communication between the game controller, e.g., a microprocessor, and the game control circuitry to a short period of time during vertical blanking of a raster scan display device. The display circuitry thereby operates substantially independently of the game details. The only game specific portion of the circuitry is contained in the permanent memory which contains the representations of the objects that are to be displayed. The game microprocessor, consequently, need only supply during vertical blanking the identities of the objects to be displayed and coordinates defining the display positions and widths of the objects to be displayed. Further independence is achieved by providing different means for clocking the microprocessor and the display circuitry, although it is entirely feasible to run both off a single basic clock.